http://www.atoppingplumbing.com 1. Check to make sure that they have a plumbing license 2. Get two or more references and read online reviews. 3. Ask how long they have been in business for. 4. Get another bid/quote for the job but make sure you are comparing apples with apples 5. Ask about their guarantee. 6. Finding a plumber who gives pricing for small jobs over the phone isn't necessarily the sign of a good plumber